The present invention relates to an intracranial pressure relief valve and, more particularly, to a pressure relief valve for shunting excess cerebrospinal fluid (CSF) from a ventricle in the brain to another location in the body of patient when epidural pressure exceeds a predetermined level.
Hydrocephalus is a condition in which the body, for any one of a variety of reasons, is unable to relieve itself of CSF which collects in the ventricles of the brain. The excessive collection of CSF in the ventricular spaces results in an increase of both epidural and intradural pressures which, in turn, causes a number of adverse pysiological effects including compression of brain tissue, impairment of blood flow in the brain tissue and impairment of the brain's normal metabolism.
Hydrocephalus is frequently treated by draining CSF in order to relieve abnormally high intracranial pressure. A variety of CSF pressure relief valves and methods of controlling CSF pressure have been developed and include various forms of check valves, servo valves or combinations thereof. Such valves generally serve to divert CSF from the ventricles of the brain through a discharge line to some suitable drainage area in the body, such as the venous system or the peritoneal cavity.
Check valves operate by simply opening when the CSF pressure differential across the valve exceeds a predetermined thresold value. Servo valves, as used in the treatment of hydrocephalus, sense intracranial pressure and open as necessary to maintain the intracranial pressure within pre-established limits.
In one CSF servo valve, described in U.S. Pat. No. 4,557,721 of the present inventor, a flexible fluid-filled bladder, hydraulically coupled to a chamber defined in part by a flexible diaphragm, was inserted into the epidural space. Changes in epidural pressure resulted in movement of the diaphragm which, in turn, controlled passage of CSF through the valve as required to maintain a desired epidural pressure.
The present invention is directed to an improved implantable servo valve for the treatment of hydrocephalus. In contrast with prior valves, the improved valve eliminates the need for a separate fluid filled bladder and instead includes an integral movable surface which directly contacts the dura-mater of the patient when the valve is installed in a burr hole through the skull.
In view of the foregoing, it is a general object of the present invention to provide a new and improved pressure regulator valve for relieving intracranial pressure caused by the excessive accumulation of CSF in the brain ventricles.
It is a more specific object of the present invention to provide a CSF pressure regulator valve which eliminates the need for a separate pressure sensor bladder.